Energy absorber for vehicle bumpers and the like

ABSTRACT

An energy absorber for vehicle bumpers and the like comprising a pair of telescopic tubular housings, with one of the housings containing a high energy spring and the other of the housings containing a fluid reservoir, whereupon impact of the vehicle bumper with an object, fluid within the reservoir is forced through a control device to effect rapid deceleration of the vehicle and compress the high energy spring.

United States Patent 1191 Fader et a1. Jan. 1, 1974 [54] ENERGY ABSORBERFOR VEHICLE 3,254,883 6/1966 Morgan 267/1 BUMPERS AND THE LIKE 3,285,59611/1966 Burgert 3,294,391 12/1966 Smith et al.... [75] Inventors: JohnH. Fader; Robert W. Hegel; 3 424 443 9 9 Chak Ma Burke A. West, all ofMonroe, 3,514,144 /1970 Alderfer Mich. 3,525,511 8/1970 Bainbridge267/64 R [73] Assignee: Monroe Auto Equipment Company, FOREIGN PATENTSOR APPLICATIONS Monroe, Mich. 581,417 10/1946 Great Britain 267/64 R[22] Filed J 1971 Primary Examiner-Gerald M. Forlenza [21] Appl. No.:148,642 Assistant Examiner-Robert Saifer Attorney-Harness, Dickey &Pierce [52] US. Cl 293/88, 267/35, 188/314 1511 1m. (:1. Br 19/06, F16f3/00 [57] ABSTRACT [58 Field of Search 213/43, 223; An gy absorber forvehicle bumpers and the like 188/266, 297, 314; 267/35, 64 R, 64 A, 64comprising a pair of telescopic tubular housings, with B, 65 R, 139 140;293]] D16, 2 70, 86, one of the housings containing a high energy spring88 89 and the other of the housings containing a fluid reservoir,whereupon impact of the vehicle bumper with an [56] Referen e Ci dobject, fluid within the reservoir is forced through a UNITED STATESPATENTS control device to effect rapid deceleration of the vehi-2.187.625 1 1940 Mercier 213/223 016 and compress the hlgh energy Sprmg2,856,035 10/1958 Rohacs 188/88 30 Claims, 4 Drawing Figures ENERGYABSORBER FOR VEHICLE BUMPERS- AND THE LIKE BACKGROUND OF THE INVENTIONIt is well known that front and rear end vehicular impact at a speed ofas low as miles per hour will cause substantial vehicle damage. In orderto mitigate the financial burden upon the public, legislation has beenproposed requiring that all automotive vehicles be able to withstand atleast a 5 mile per hour barrier impact without incurring any appreciabledamage. In order to come within the regulations of such legislation,most automobile manufacturers are contemplating the use of high impactenergy absorbers at at least the front end, and eventually at both thefront and rear ends, of vehicles to be manufactured in the future.

While there has been a wide variety of different types of energyabsorbers known in the prior art which have been capable, at least tosome degree, of absorbing the high impact energy created in a vehiclecollision, most, if not all, such prior known devices have beenincapable of satisfying the strict design criteria that has beenestablished. In particular, due to certain design com promises in modernautomotive vehicles, there is a maximum impact force that a vehicle canwithstand without component failure occurring. This could be a bumperbolt or engine mount shearing, for example, as well as a myriad of manyother things; The automotive industry has indicated amaximum allowableforce that can be transmitted to a basic frame or chassis structure isin the range of 10,000 to l2,000 pounds. The energy to stop a fourthousandpound mass (weight of a typical automotive vehicle) moving at avelocity of 5 miles per hour, or 7.33 feet per second, is 40,000inch-pounds, and where l0,000 pounds is the maximum allowable force orload which can be incurred by the vehicle per energy absorbing unit, andwhere two units are used, a square force displacement curve is requiredhaving a 2-inch stroke. As previously mentioned, prior known energyabsorbing devices which would be economically feasible on modern massproduced automotive vehicles have been incapable of absorbing ordissipating a 10,000 pound force in a 4-inch stroke and as such, fallfar short of satisfying the established operational requirements. I

SUMMARY OF THE INVENTION The present invention relates to an energyabsorber unit which has been found to exhibit considerably superioroperating characteristics, as compared with the various analogousdevices known in the prior art; more importantly, however, the presentinvention has been found to readily satisfy the established designcriteria, i.e., of absorbing the impact force of a 5 mile per hourcollision in approximately a 3-inch stroke. Generally speaking, theenergy absorber of the present invention comprises a pair ofconcentrically oriented, telescopic tubular housings, one of whichcontains a high energy spring, and the other of which contains a fluidreservoir and means defining a flow orifice for communicating fluid intothe housing containing the spring. Upon impact, the two housingstelescope, whereby fluid is forced through the orifice whichiscalibrated so that approximately the maximum specified system force iscaused. This restraining force causes the vehicle to begin todecelerate; however, as the velocity decreases, so does the hydraulicforce. For this reason, after the fluid passes through the orifice, itfunctions to compress the high energy spring, with the result that thespring force increases concomitantly with a decrease in the hydraulicsource, thus approximating the maximum allowable restraining forcethrough the stroke. As will hereinafter be described in detail, the highenergy spring is designed so that it will force the hydraulic fluid backinto the reservoir, as well as return the unit to its original extendedposition, with the result that the energy absorber of the presentinvention is entirely selfresetting preparatory a subsequent collisionor impact.

It is accordingly a general object of the present invention to provide anew and improved energy absorber for use in operative association withautomotive vehicle bumpers and the like.

It is a more particular object of the present invention to provide a newand improved energy absorber which utilizes both hydraulics and a highenergy spring.

It is yet a more particular object of the present invention to provide ahigh energy absorber unit which utilizes a micro cellular fluidimpervious spring.

It is another object of the present invention to provide an energyabsorber which is of a strong, durable construction and is capable ofabsorbing high impact energy with a minimum stroke.

It is yet another object of the present invention to provide an energyabsorber which may be subjected to substantial bending forces as mightoccur when a vehicle is jacked-up by its associated bumper.

It is still another object of the present invention to provide an energyabsorber unit wherein the high energy spring acts to vary the dischargecoefficient of the flow control orifice.

It is yet a further object of the present invention to provide a new andimproved energy absorber which is both velocity and displacementsensitive.

It is another object of the present invention to provide a new andimproved energy absorber of the above described type wherein the unitbottoms out on the high energy spring to'prevent damage to thetelescopic housings during an impact absorbing cycle.

It is still a further object of the present invention to provide anenergy absorber of the above described type including a housing which iscapable of expanding in order to absorb impact energy in excess of thedesign capacity of the unit.

It is still a further object of the present invention to provide anenergy absorber which is of a simple design, is economical tomanufacture and easy to install.

Other objects and advantages of the present invention will becomeapparent from the following detailed description taken in conjunctionwith the accompanying drawing.

APPLICABLE PRIOR ART The following patents are believed to be pertinentwith regard to the subject matter disclosed and claimed herein:

Patent No. Inventor Date 3,424,448 F. T. Chak Ma 1/28/60 3,525,5[1 W. N.Bainbridge 8/25/70 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is anelevated perspective view of a pair of energy absorber units constructedin accordance with the present invention and shown in operativeassociation with a schematic representation of a portion of aconventional automotive vehicle;

FIG. 2 is an enlarged longitudinal cross-sectional view of one of theenergy absorber units shown in FIG.

FIG. 3 is a fragmentary cross-sectional view of a slightly modifiedembodiment of the fluid flow control portion of the energy absorber unitshown in FIG. 2; and

FIG. 4 is a fragmentary view of yet another embodiment of the flowcontrol portion of the energy absorber unit shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG.1 of the drawing, a schematic representation of a vehicle frame orchassis is representatively designated by the numeral 10 and is shown ascomprising a pair of longitudinally extending spaced parallel framemembers 12 and 14. Extending laterally or transversely of the vehicleframe 10 at one end thereof is a conventional vehicle bumper, generallydesignated 16. In accordance with the present invention, the bumper 16is adapted to be operatively supported upon the frame members 12 and 14by means of a pair of energy absorber units, generally designated by thenumeral 20, the units 20 generally functioning to absorb the impactenergy created upon engagement of the bumper 16 with an object atrelatively low vehicle speeds, i.e., in the order of to miles per hour,whereby to prevent the impact energy from being transmitted to the frame10 and thus minimize damage to the vehicle. It will be appreciated thatthe bumper 16 may be located at the front or rear of the associatedvehicle and that the energy absorber units 20 may therefore be utilizedin absorbing the impact energy of both front and rear end collisions. Byvirtue of the fact that the units 20 associated with the bumper 16 areidentical in construction and operation, the following detaileddescription of one of said units will be applicable to either of thoseshown in FIG. 1, as will be apparent to those skilled in the art.

As best illustrated in FIG. 2, the energy absorber unit 20 of thepresent invention comprises an elongated cylindrical tube or housingmember 22 which is adapted to be fixedly secured to the associated ofthe frame members 12 or 14 by means of an annular attachment ring 24'.The ring 24 extends around the outer periphery of the housing member 22and comprises a generally axially extending section 26 adapted to besecured, as by welding, to the outer periphery of the member 22 adjacentthe end thereof confronting the bumper 16. The attachment ring 24comprises a radially outwardly extending section 28 which is formedintegrally of the section 26 and is formed with a plurality of axiallyextending apertures 30. The attachment ring 24 is adapted to be fixedlysecured to a suitable mounting bracket or the like 32 secured by meansof suitable screws, bolts or the like 34 to the associated frame member12 or 14. The mounting bracket 32 is formed with a central, largediameter opening 35 through which the inner end of the unit 20 extends,as best seen in FIG. 2. Additionally, the bracket 32 is formed with aplurality of apertures 36 which are adapted for alignment with theapertures 30 of the attachment ring 24, whereby a plurality of suitablescrews, bolts or the like 38 may be inserted through the respectivepairs of aligned apertures 30, 36 and be provided with conventional nuts40 for operatively securing the attachment ring 24 to the mountingbracket 32 and hence secure the energy absorber unit 20 to the vehicleframe 10.

The energy absorber unit 20 of the present invention comprises a secondelongate cylindrical housing member 42 which is slightly smaller indiameter than the member 22 and is adapted to be telescopically receivedtherewithin, as best seen in FIG. 2. One end of the housing member 42 isprovided with an end plate member 44 comprising a central annularembossed portion 46 that is adapted to be nestingly inserted into theadjacent end of the housing member 42 for properly orienting orpositioning the members 42, 44. The end plate member 44 is adapted to befixedly secured to the adjacent end of the housing member 42 by means ofwelding or the like designated by the numeral 48, and the member 44comprises an outwardly extending peripheral flange section 50 which isformed with a plurality of apertures 52. The member 44 is adapted to befixedly secured to the associated vehicle bumper 16 by means of asuitable mounting bracket 54 comprising a central or intermediatesection 56 that is adapted to be secured to the interior side of thebumper 16 by means of suitable screws, bolts or the like 58 and nuts 60.The upper and lower ends of the bracket 54 comprise intumed, generallycoplanar flanges 62 and 64 which are formed with suitable apertures 66adapted for alignment with the apertures 52, whereby suitable screws,bolts or the like 68 may be inserted through the aligned apertures 52,66 and be provided with nuts 70 to operatively secure the adjacent endof the energy absorber unit 20 to the bumper 16.

While the above described manner of operatively securing the housingmembers 22, 42 to the vehicle frame 10 and bumper 16 has been found tobe highly satisfactory and preferable for purposes of simplicity ofmanufacture, assembly and installation, it will be appreciated thatvarious alternative means may be utilized in operatively mounting theenergy absorber unit 20 without departing from the scope or fair meaningof the present invention.

Referring still to FIG. 2, the end of the housing member 22 opposite theattachment ring 24 is provided with an end closure plate 72 which isadapted to be secured as by welding 74 within the end of the member 22and thereby define one end of a variable volume cylindrical fluidchamber or reservoir, generally designated 76. The opposite end of thechamber 76 is defined by an annular end plate 78 that is formed with acentral axially extending orifice 80 which communicates at one endthereof with the chamber 76. The end plate 78 is adapted to be fixedlysecured to the adjacent end of the housing member 42 by having said endswaged around the outer periphery of the plate 78, as seen at 82, withthe swaged end portion 82 being formed with a radially inwardlyextending lip portion 84 which overlies the radial face of the end plate78 confronting the chamber 76. The end plates 46 and 78, along with thehousing member 42, define a second cylindrical chamber, generallydesignated by the numeral 86, which is communicable via the orifice 80with the chamber 76 and is adapted to receive hydraulic fluid, such asoil or the like from the chamber 76 to control or dampen longitudinaltelescopic movement of the housing member 42 with respect to the member22 and thereby operate to absorb or dissipate impact energy created uponengagement of the bumper 16 with an object, as will hereinafter bedescribed in detail.

In order to assure against any axial misalignment between the housingmembers 22, 42 upon relative longitudinal telescopic movementtherebetween and also to provide a strong durable construction, theswaged portion 82 on the one end of the housing member 42 is formed withan annular cylindrical surface 88 that is substantially the samediameter as the inner diameter of the housing member 22 and is adaptedfor longitudinal sliding engagement therewith. The surface 88 iscooperable with a cylindrical spacer ring 90 which extends around theouter periphery of the housing member 42 and is secured thereto, as bywelding 92, at a position preferably, but not necessarily, equidistantfrom the opposite ends thereof. The-ring 90 defines an outer cylindricalsurface 94 which is of the same diameter of the surface 88 and with thesurface adapted for sliding engagement with the inner periphery of thehousing member 22. It will be noted that the axial end of the housingmember 22 adjacent the bumper 16 is tapered or swaged inwardly as seenat 96, whereby to limit longitudinal outward unit of the housing member42 with respect to the housing member 22, as will be apparent.Additionally, it will be seen that the suitable cup-type fluid seal 98is provided adjacent the spacer ring 90 between the inner periphery ofthe housing member 22 and the outer periphery of the housing member 42,whereby to provide against fluid leakage. It will also be noted that theabove described construction assures that the unit may be subjected toconsiderable bending forces, as might occur when a collision occursbetween vehicles having misaligned bumpers or when the associatedvehicle is being jacked up by the bumper 16.

In accordance with the present invention, and as previously stated, thevariable volume chamber 76 is adapted to be provided with a quantity ofhydraulic fluid, which fluid, upon telescopic inward movement of thehousing member 42, will be forced through the orifice 80 and into thechamber 86. Such fluid is adapted to be cooperable with a non-linearhigh energy spring means which is contained within the chamber 86 indamping or dissipating impact energy. The high energy spring, inaccordance with the present invention, comprises an elongated,cylindrical cartridge, generally designated by the numeral 100, that isfabricated of a resilient elastomeric material which is adapted to becompressed by the aforesaid fluid as it is forced from the chamber 76through the orifice 80 into the chamber 86, with the result that theimpact energy is absorbed not only by the resistance to fluid flowthrough the orifice 80, but also by the inherent resilientcharacteristics of the cartridge 100, as will be described in connectionwith the overall operation of the energy absorber unit 20.

While the cartridge 100 may be fabricated of a wide variety of differenttypes of resilient elastomeric materials, such as various types of wellknown material or synthetic rubbers, the cartridge 100 is preferablyfabricated of a micro cellular resilient material, preferably, aflexible urethane elastomer, which is of a type adapted to withstand oilabsorption and provide the desired non-linear spring characteristics.The specific type of urethane material which has been found to be highlysatisfactory consists of an open-celled or articulated flexiblepolyurethane foam having an integral oil impervious skin which completlyencloses the cartridge to insure against oil absorption. It will beappreciated that while an integral fluid impervious skin is preferableon the cartridge 100, various other types of fluid impervious barrierscould be used, such as a polyethylene enclosure, or the like.

It will be seen that the cartridge 100 substantially fills the chamber86 with the cartridge 100 havinga first end portion 102 which bearsagainst the. end plate member 44, and an opposite end portion 104 whichbears against the end plate 78. If desired, the cartridge 100 may bemade slightly oversized so that when it is assembled between the plates46, 78, the cartridge 100 will be slightly compressed or preloaded inorder to achieve certain desired operational characteristics.

Referring now to the overall operation of the energy absorber unit 20 ofthe present invention, the unit 20, as well as the associated unit 20located at the opposite end of the bumper 16, is normally disposed inits extended configuration shown in FIG. 2. At such time as the bumper16 is subjected to an impact force, for example, in the event anassociated vehicle collides with an object, the bumper 16 as well as thehousing member 42 will be biased toward the right in FIG. 2. When thisoccurs, the volume of the chamber 76 will be reduced and the hydraulicfluid therewithin will be forced out of the chamber 76 thorugh theorifice 80 into the chamber 86 containing the cartridge 100. The size ofthe orifice is calibrated so that a preselected force to telescopicmovement of the housing member 42 relative to the housing member 22 isachieved. Such force is typically in the order of ten to twelve thousandpounds, which force, of course, causes the vehicle to rapidly begin todecelerate, and at the same time, the fluid which is flowing through theorifice 80 into the chamber 86 causes the cartridge to be compressed,thereby causing further deceleration of the vehicle. A unique feature ofthe present invention resides in the fact that as the velocity of thevehicle decreases, so does the hydraulic force, or force created by thefluid flowing through the orifice 80; however, as the hydraulic forcedecreases, the cartridge 100 is becoming further compressed resulting inan increased spring force which complements the decreasing hydraulicforce to provide an approximately constant displacement curve whichenables the entire impact force to be dissipated in a very shortdistance, such as in the order of approximately 3 inches. The reason forthis resides in the fact that both the cartridge 100 and orifice 80provide nonlinear resistance forces which are complementary to oneanother and result in a relatively constant overall or total resistanceforce. A noteworthy feature of the present invention resides in the factthat the axial dimension of the cartridge 100 may be and preferably isselected such that when the cartridge 100 is completely or nearlycompletely compressed, there is no bottoming out and thus there is nometal to metal contact between the members 72, 78 which might result inexcessive damage to the vehicle frame or chassis. Due to the particularnon-linear performance characteristics of the cartridge 100, there is agradual increase in the resistance force provided thereby at theapproximate time the cartridge 100 is nearly compressed. This increasein force is found to be desirable to prevent a sudden change inresistant force which would occur when the cartridge reaches its fullycompressed condition during an energy absorbing cycle. Another featureof the present invention resides in the fact that the wall thickness ofthe housing members 22, 42 may be selected such that in the event thebumper 16 engages an object with an impact force in excess of the designcapacity of the unit 20, the walls of the members 22, 42 will bulge ordeform outward slightly, whereby to absorb additional impact energy andthus prevent such additional energy being transmitted to the vehicleframe or chassis 10.

After the impact force or energy has been dissipated by the unit 20resulting in the cartridge 100 being compressed, the natural resilientcharacter of the material constituting the cartridge 100 will force thehydraulic fluid within the chamber 86 back through the orifice 80 intothe chamber 76 and return the unit 20 to its extended position shown inFIG. 2 to prepare the vehicle for a subsequent collision or other sourceof high impact energy.

In certain instances, it may be desirable to provide a threshold forceto telescopic movement of the housing member 42 with respect to themember 22. In accordance with the present invention, such means may beprovided by a valve arrangement for initially preventing fluid flow fromthe chamber 76 through the orifice 80 into the chamber 86. Such valvemeans would typically operate as a hold-off" valve to prevent fluid flowthrough the orifice 80 until a predetermined impact force is exertedagainst the bumper 16. By way of example, the typical valve means isrespectively illustrated in FIG. 3 and generally designated as a valveassembly 106. The assembly 106 is shown operatively mounted within thechamber 86 and comprises a valve member 108 which is adapted to bebiased into engagement with the end plate 78 by a suitable valve spring1 10, whereby to block fluid flow through the orifice 80. Both the valvemember 108 and valve spring 110 are operatively mounted within asuitable valve cage or enclosure 112 which comprises a central cupshaped portion 114 and a peripheral flange portion 116. As illustrated,the enclosure 112 is operatively received within a suitable annularrecess 118 formed in the adjacent end of the cartridge 100. The flangeportion 116 is formed with a plurality of fluid flow orifices 120 whichare communicable via a suitable annular recess 122 formed in the face ofthe enclosure 112 confronting the end plate 78, whereby when the valvemember 108 is disposed in a retracted or open position against theresistance of the spring 110, fluid may flow through the orifice 80,recess 122 and orifices 120 into the chamber 86. It will be noted thatthe valve member 108 may be formed with a central bore 124 whichcommunicates through an aligned bore 126 in the enclosure 112. Thereason for the bores 124, 126 is that at the beginning of an energyabsorbing cycle, there is a substantially large pressure drop across thevalve member 108 and thus a pressure drop across the bore 126.Accordingly, as pressure builds up within the chamber 86, the pressuredrop across the orifice 126 decreases, allowing the spring 110 to startclosing the valve member 108; this, in turn, prevents the forceresisting compression of the unit 20 from being decreased due to reducedvelocity. A suitable bore 128 may be and preferably is formed in the endplate 78 in alignment with the recess 122,

which bore 128 may be provided with a suitable oneway check valve or thelike 130 which functions to communicate fluid back to the chamber 76after each energy absorbing cycle.

It will be seen that when the energy absorber unit 20 is provided withthe valve assembly 106, fluid will be prevented from flowing into thechamber 86 until the force of the spring 1 10 is overcome. This springorifice combination may be calibrated to any degree of force, dependingupon the desired operational characteristics of the unit 20. It may benoted, of course, that the spring 110 need not be of the coil or helicaltype illustrated herein, since it could be fabricatedof an elastomericmaterial such as rubber, urethane or the like, where size and capacitydictate.

With reference to FIG. 4, for certain operative installations, it may bedesirable to utilize the valve assembly 106, as above described, inconjunction with an additional flow orifice, such as that designated bythe numeral 132 which would function with the cartridge 100 to give acloser approximation of a square or constant force displacement curve.

It will be seen from the foregoing that the present invention provides anovel energy absorber unit which is designed to overcome the myriad ofproblems in connection with prior known devices, as well as satisfy therigorous demands of the automotive industry. A particular feature of thepresent invention resides in the fact that relatively high impact energycan be absorbed with a very short or small degree of telescopic movementof the housing members 22, 42, whereby the unit 20 may be installedwithout seriously affecting the aesthetic appearance of the associatedvehicle.

Another feature of the present invention resides in the fact that asfluid is forced from the chamber 76 through the orifice into the chamber86, in order to effect compression of the cartridge 100, the end of thecartridge adjacent the orifice 80 will move away therefrom at apredetermined rate, depending primarily upon the size of the orifice andphysical characteristics, i.e., density, etc., of the cartridge 100. Byproperly selecting the material from which the cartridge 100 isfabricated, as well as properly designing the physical dimensions of thehousing members 22, 42 and orifice 80, the end portion 104 of thecartridge 100 will function to vary the discharge coefficient of theorifice 80 as it moves away from the end plate 78 during an energyabsorbing cycle. Another feature of the present invention resides in thefact that the unit 20 will be formed to be of an extremely strong anddurable construction, will require relatively small tooling costs andwill have a long and effective operational life.

While it will be apparent that the preferred embodiments illustratedherein are well calculated to fulfill the objects above stated, it willbe appreciated that the present invention is susceptible tomodification, variation and change without departing from the scope ofthe invention.

We claim:

1. In an energy absorbing unit,

a first generally cylindrical housing member,

a second generally cylindrical housing member adapted for telescopicengagement with said first member,

means defining a fluid chamber in one of said members and a flow controlorifice communicating said chamber with the other of said members,

a high energy; spring disposed in said other housing member,

said spring being fabricated of resilient elastomeric cellular materialand comprising an elongated cylindrical body of substantially the samecrosssectional size as the interior of said other housing member andoccupying substantially the entire interior volume thereof, whereby thelongitudinally opposite ends of said body are disposed directly adjacentthe ends of said other housing member, whereby any fluid transmittedthrough said orifice into said other housing results in compression ofsaid body, with the resistance to compression of said spring and theresistance to fluid flow through said orifice being complementary andproviding a relatively constant overall resistant force.

2. The invention as set forth in claim 1 which includes valve means forcontrolling fluid flow from said chamber to said other housing member.

3. The invention as set forth in claim 1 which includes means forvarying the discharge coefficient of said orifice.

4. The invention as set forth in claim 1 which includes first and secondorifice means communicating said chamber with said other housing member.

5. The invention as set forth in claim 4 which includes valve means forcontrolling fluid flow through one of said orifices, said valve meansacting as a holdoff means to prevent compression of said spring until apreselected fluid pressure is achieved.

6. The invention as set forth in claim 1 wherein said spring isnon-linear.

7. In a device for absorbing the impact energy of a ve hicle bumper,

an elongated cylindrical housing comprising first and second generallyaxially aligned telescopic housing sections,

a non-linear high energy absorbing spring occupying a portion of saidhousing,

a fluid chamber occupying the remaining portion of said housing,

fluid flow control means disposed between said chamber and said springthrough which fluid may flow from said chamber to effect compression ofsaid spring,

means extending generally transversely of one of said housing sectionsand movable axially therewithin for varying the operationalcharacteristics of said fluid control means, and

means for operatively supporting said device at a position wherein saidspring is adapted to absorb the impact force transmitted to the vehiclebumper upon engagement thereof with an object.

8. The invention as set forth in claim 7 wherein said fluid flow controlmeans includes means defining an orifice through which fluid flows tocompress said spring, and wherein said operational characteristicvarying means includes means for varying the discharge coefficient ofsaid orifice.

9. The invention as set forth in claim 8 wherein a portion of said bodyis operable to vary the discharge coefficient of said orifice.

10. The invention as set forth in claim 7 which includes means providinga fluid impervious barrier around said body.

11. The invention as set forth in claim 10 wherein said barriercomprises an integral fluid impervious skin on said body.

12'. An energy absorbing unit comprising a first elongated tubularhousing having means defining an orifice at one end thereof,

a cylindrical resilient elastomeric member disposed within said housingand occupying substantially the entire interior volume thereof, with oneend of said member being disposed directly adjacent said orifice andacting to prevent the free flow of fluid therethrough,

a second tubular housing telescopically movable relative to said firsthousing and defining a fluid chamber, a quantity of fluid in saidchamber adapted to be forced through said orifice upon telescopicmovement of said first and second housings, and

means including said one end of said member providing for a variabledischarge coefficient' of fluid flow through said orifice.

13. The invention as set forth in claim 12 wherein said last mentionedmeans includes a radially disposed end of said member movable inresponse to compression of said elastomeric member toward and away fromsaid orifice.

14. The invention as set forth in claim 12 wherein said elastomericmember is fabricated of a flexible urethane elastomer.

15. The invention as set forth in claim 12 which includes valve meansfor controlling fluid flow through said orifice.

16. In an energy absorbing unit,

a first generally cylindrical housing member,

a first element at one end of said member,

a second generally cylindrical housing member telescopically movablerelative to said first member,

a fluid chamber in one of said members and means including a secondelement at the opposite end of said first housing member from said firstelement defining a flow control orifice communicating said chamber withthe other of said members,

a quantity of fluid in said chamber,

a high energy spring disposed in said other of said housing member andadapted to be compressed under the influence of fluid communicated fromsaid chamber through said orifice into said other member,

said spring comprising a resilient elastomeric cellular body of agenerally cylindrical configuration normally occupying substantially theentire interior volume of said first housing member and having theaxially opposite ends juxtapositioned said first and second elements,and

means including said spring for controlling the flow of fluid from saidchamber into said other housing member, whereby fluid will not flow fromsaid chamber into said first housing member until preselectedtelescoping movement occurs between said first and second housingmembers.

17. The invention as set forth in claim 16 wherein said valve meanscomprises a valve member, and means resiliently urging said valve membertoward a position closing said orifice.

18. The invention as set forth in claim 17 which includes means forsupporting said valve member and said resilient means adjacent saidorifice.

19. The invention as set forth in claim 18 wherein said support meanscomprises a valve cage.

20. The invention as set forth in claim 16 wherein said valve meanscomprises check valve means for controlling flow from said other memberto said chamber.

21. The invention as set'forth in claim 16 which includes meanscommunicating said chamber with said other member other than saidorifice for permitting fluid flow from said chamber to said other memberat energy levels lower than that necessary to open said valve means.

22. In an energy absorbing unit,

a first generally cylindrical housing member,

a second generally cylindrical housing member adapted for telescopicengagement with said first member,

means defining a fluid chamber in one of said members and a flow controlorifice communicating said chamber with the other of said members,

a high energy spring disposed in said other of said housing member andadapted to be compressed under the influence of fluid communicated fromsaid chamber,

said spring being fabricated of a resilient elastomeric cellularmaterial and being of an elongated cylindrical configuration having oneend thereof disposed adjacent said orifice, and

valve means for controlling the flow of fluid from said chamber intosaid other housing member, whereby said spring will not be compressed bysaid fluid until the pressure of said fluid reaches a predeterminedlevel, said one end of said spring being of a generally complementaryconfiguration with respect to said valve means.

23. An energy absorber comprising,

a first hollow cylindrical housing member having an interior chamberdefined at one end thereof by support means for said housing member andat the opposite end thereof by an orifice defining element,

a compressible spring in said first housing member and occupyingsubstantially the entire volume of said chamber,

a second hollow cylindrical housing member telescopically supportedrelative to said first member and having mounting means at one endthereof,

a fluid compartment within said second housing member and defined bysaid mounting means thereof and said orifice defining element, and

means for compressing said spring in response to fluid flowing from saidcompartment through said orifice into said chamber.

24. The invention as set forth in claim 23 which includes a valve forcontrolling fluid flow through said orifice.

25. The invention as set forth in claim 24 wherein said spring comprisesa generally radially disposed end portion located directly adjacent saidelement when said spring is in a non-compressed condition, and whereinsaid surface is cooperable with said orifice in varying the dischargecoefficient thereof.

26. In an energy absorbing unit,

a housing including first and second sections,

first force damping means including a quantity of fluid in said firstsection, a restricted orifice defining member separating said sections,and second force damping means including a compressible spring disposedin said second section and adapted to be compressed by fluid passingthrough the orifice in said member, means in said second sectionnormally disposed adjacent said orifice for preventing the free flow offluid from said first section through said orifice to said secondsection,

first and second generally tubular telescopic housing members, one ofsaid members defining a fluid reservoir and the other of said membersadapted to contain said spring,

the damping force of said second damping means increasing atapproximately the same rate as the damping force of said first dampingmeans decreases, whereby a substantial constant resultant damping forceis provided.

27. The invention as set forth in claim 26 which includes means forresisting fluid flow through said orifice until a preselected force isexerted against said unit.

28. The invention as set forth in claim 27 which includes valve meansfor controlling fluid flow through said orifice.

29. The invention as set forth in claim 26 wherein said spring isfabricated of a flexible urethane elastomer.

30. The invention as set forth in claim 29 wherein said spring comprisesa generally cylindrically shaped cartridge.

1. In an energy absorbing unit, a first generally cylindrical housing member, a second generally cylindrical housing member adapted for telescopic engagement with said first member, means defining a fluid chamber in one of said members and a flow control orifice communicating said chamber with the other of said members, a high energy spring disposed in said other housing member, said spring being fabricated of resilient elastomeric cellular material and comprising an elongated cylindrical body of substantially the same cross-sectional size as the interior of said other housing member and occupying substantially the entire interior volume thereof, whereby the longitudinally opposite ends of said body are disposed directly adjacent the ends of said other housing member, whereby any fluid transmitted through said orifice into said other housing results in compression of said body, with the resistance to compression of said spring and the resistance to fluid flow through said orifice being complementary and providing a relatively constant overall resistant force.
 2. The invention as set forth in claim 1 which includes valve means for controlling fluid flow from said chamber to said other housing member.
 3. The invention as set forth in claim 1 which includes means for varying the discharge coefficient of said orifice.
 4. The invention as set forth in claim 1 which includes first and second orifice means communicating said chamber with said other housing member.
 5. The invention as set forth in claim 4 which includes valve means for controlling fluid flow through one of said orifices, said valve means acting as a hold-off means to prevent compression of said spring until a preselected fluid pressure is achieved.
 6. The invention as set forth in claim 1 wherein said spring is non-linear.
 7. In a device for absorbing the impact energy of a vehicle bumper, an elongated cylindrical housing comprising first and second generally axially aligned telescopic housing sections, a non-linear high energy absorbing spring occupying a portion of said housing, a fluid chamber occupying the remaining portion of said housing, fluid flow control means disposed between said chamber and said spring through which fluid may flow from said chamber to effect compression of said spring, means extending generally transversely of one of said housing sections and movable axially therewithin for varying the operational characteristics of said fluid control means, and means for operatively supporting said device at a position wherein said spring is adapted to absorb the impact force transmitted to the vehicle bumper upon engagement thereof with an object.
 8. The invention as set forth in claim 7 wherein said fluid flow control means includes means defining an orifice through which fluid flows to compress said spring, and wherein said operational characteristic varying means includes means for varying the discharge coefficient of said orifice.
 9. The invention as set forth in claim 8 wherein a portion of said body is operable to vary the discharge coefficient of said orifice.
 10. The invention as set forth in claim 7 which includes means providing a fluid impervious barrier around said body.
 11. The invention as set forth in claim 10 wherein said barrier comprises an integral fluid impervious skin on said body.
 12. An energy absorbing unit comprising a first elongated tubular housing having means defining an orifice at one end thereof, a cylindrical resilient elastomeric member disposed within said housing and occupying substantially the entire interior volume thereof, with one end of said member being disposed directly adjacent said orifice and acting to prevent the free flow of fluid therethRough, a second tubular housing telescopically movable relative to said first housing and defining a fluid chamber, a quantity of fluid in said chamber adapted to be forced through said orifice upon telescopic movement of said first and second housings, and means including said one end of said member providing for a variable discharge coefficient of fluid flow through said orifice.
 13. The invention as set forth in claim 12 wherein said last mentioned means includes a radially disposed end of said member movable in response to compression of said elastomeric member toward and away from said orifice.
 14. The invention as set forth in claim 12 wherein said elastomeric member is fabricated of a flexible urethane elastomer.
 15. The invention as set forth in claim 12 which includes valve means for controlling fluid flow through said orifice.
 16. In an energy absorbing unit, a first generally cylindrical housing member, a first element at one end of said member, a second generally cylindrical housing member telescopically movable relative to said first member, a fluid chamber in one of said members and means including a second element at the opposite end of said first housing member from said first element defining a flow control orifice communicating said chamber with the other of said members, a quantity of fluid in said chamber, a high energy spring disposed in said other of said housing member and adapted to be compressed under the influence of fluid communicated from said chamber through said orifice into said other member, said spring comprising a resilient elastomeric cellular body of a generally cylindrical configuration normally occupying substantially the entire interior volume of said first housing member and having the axially opposite ends juxtapositioned said first and second elements, and means including said spring for controlling the flow of fluid from said chamber into said other housing member, whereby fluid will not flow from said chamber into said first housing member until preselected telescoping movement occurs between said first and second housing members.
 17. The invention as set forth in claim 16 wherein said valve means comprises a valve member, and means resiliently urging said valve member toward a position closing said orifice.
 18. The invention as set forth in claim 17 which includes means for supporting said valve member and said resilient means adjacent said orifice.
 19. The invention as set forth in claim 18 wherein said support means comprises a valve cage.
 20. The invention as set forth in claim 16 wherein said valve means comprises check valve means for controlling flow from said other member to said chamber.
 21. The invention as set forth in claim 16 which includes means communicating said chamber with said other member other than said orifice for permitting fluid flow from said chamber to said other member at energy levels lower than that necessary to open said valve means.
 22. In an energy absorbing unit, a first generally cylindrical housing member, a second generally cylindrical housing member adapted for telescopic engagement with said first member, means defining a fluid chamber in one of said members and a flow control orifice communicating said chamber with the other of said members, a high energy spring disposed in said other of said housing member and adapted to be compressed under the influence of fluid communicated from said chamber, said spring being fabricated of a resilient elastomeric cellular material and being of an elongated cylindrical configuration having one end thereof disposed adjacent said orifice, and valve means for controlling the flow of fluid from said chamber into said other housing member, whereby said spring will not be compressed by said fluid until the pressure of said fluid reaches a predetermined level, said one end of said spring being of a generally complementary configuration with rEspect to said valve means.
 23. An energy absorber comprising, a first hollow cylindrical housing member having an interior chamber defined at one end thereof by support means for said housing member and at the opposite end thereof by an orifice defining element, a compressible spring in said first housing member and occupying substantially the entire volume of said chamber, a second hollow cylindrical housing member telescopically supported relative to said first member and having mounting means at one end thereof, a fluid compartment within said second housing member and defined by said mounting means thereof and said orifice defining element, and means for compressing said spring in response to fluid flowing from said compartment through said orifice into said chamber.
 24. The invention as set forth in claim 23 which includes a valve for controlling fluid flow through said orifice.
 25. The invention as set forth in claim 24 wherein said spring comprises a generally radially disposed end portion located directly adjacent said element when said spring is in a non-compressed condition, and wherein said surface is cooperable with said orifice in varying the discharge coefficient thereof.
 26. In an energy absorbing unit, a housing including first and second sections, first force damping means including a quantity of fluid in said first section, a restricted orifice defining member separating said sections, and second force damping means including a compressible spring disposed in said second section and adapted to be compressed by fluid passing through the orifice in said member, means in said second section normally disposed adjacent said orifice for preventing the free flow of fluid from said first section through said orifice to said second section, first and second generally tubular telescopic housing members, one of said members defining a fluid reservoir and the other of said members adapted to contain said spring, the damping force of said second damping means increasing at approximately the same rate as the damping force of said first damping means decreases, whereby a substantial constant resultant damping force is provided.
 27. The invention as set forth in claim 26 which includes means for resisting fluid flow through said orifice until a preselected force is exerted against said unit.
 28. The invention as set forth in claim 27 which includes valve means for controlling fluid flow through said orifice.
 29. The invention as set forth in claim 26 wherein said spring is fabricated of a flexible urethane elastomer.
 30. The invention as set forth in claim 29 wherein said spring comprises a generally cylindrically shaped cartridge. 